Crystal detector



Aug. 4, 1925. 1,548,408

- N. B. DAYIS CRYSTAL DETECTOR Filed 001:. 18, 1924 INVENTOR= v N' B' DAVIS' Wad 44 I A'ITORNEYS' Fatentecl Aug. 4, 1925.

UNITED STATES NORMAN BRUCE DAVIS, 0F OTTAWA, ONTARIO, CANADA.

CRYSTAL DETECTOR.

Application filed October 18, 1924. Serial No. 744,424.

T 0 all whom it may concern Be it known that I, NORMAN BRUCE DAVIS, a citizen of the Dominion of Canada, residing at 224 Second Avenue, in the city of Ottawa, Province of Ontario, Canada, having invented certain new and useful Improvements in Crystal Detectors, do hereby declare that the following is a full, clear, and exact description of the same.

. This invention relates to crystal detectors for use in radioreceivers and particularly to those of the class known as adjustable crystal detectors.

The invention has for its object to provide an improved detector of this general class and which can be manufactured cheaply and easily from a small number of simple parts. The invention also makes it possible to manufacture a detector which is small in size, attractive in appearance and unitary in structure, and in which the crystal adapts itself with certainty to adjusted position and at the same time is always effectively shielded from extraneous influences which might cause corrosion.

According to the present invention the crystal floats upon a body of mercury. An adjustable contact, such as the end of a screw, presses upon the top of the crystal so that the mercury, by reason of its superior specific gravity, acts as a cushion and maintains the crystal in yieldable contact with the screw.

A convenient embodiment of the invention will now be described with reference to the accompanying drawings, in which Figure 1 is a vertical sectional elevation,

Figure 2 is a cross section on the line 22 of Figure 1, and

Figure 8 is a fragmentary section illustrating a modified means for mounting the detector.

The crystal a floats upon a globule of mercury b which lies at the bottom of a casing formed by a tube 0 of glass or other suitable insulating substance, fitted into a recess in a member at of metal such as aluminium, which is not affected by mercury. A cap 6 is fitted on the top of the tube a, the tube being cemented into the upper and lower members at and e as atf.

The cap e is axially threaded to receive a screw 9 which extends down the tube 0 and preferably has a rounded or pointed extremity which contacts with the crystal a. By screwing down the screw 9 the crystal is caused to displace the mercury and the upward thrust of the dispaced mercury maintains the crystal in contact with the screw with pressure which will remain substantially constant.

Any suitable means may be employed for mounting the detector, for example, a pair of spaced clips h mounted on a panel 7; by terminal screws j and engaging the caps cl and 6 may be used as shown in Figures 1 and 2 or either the members (Z or e or both may have an integral stud 70 which passes through the panel and acts as a terminal as shown in Figure 3.

A suitable device is preferably provided for locking the screw in its adjusted position, and this may conveniently take the form of a coil spring Z compressed between the cap 6 and head of screw 9, as shown in Figure 1.

Any crystal which is uniformly, or substantially uniformly, sensitive at all points of its surface may be used and the term crystal is used in this sense in the appended claims.

What I claim is l. A crystal detector comprising a body of mercury, a crystal floating on the mercury and a vertically adjustable conducting member contacting with the top surface of the crystal.

2. A crystal detector comprising a tube of insulating material, metallic caps secured on the ends of the tube, a globule of mercury at the bottom of said tube, a crystal floating on the mercury and a screw threaded member engaging a threaded hole in the upper cap and extending down the tube into contact with the crystal.

3. A crystal detector comprising a tube of insulating material, metallic caps having re cesses into which said tube is cemented, a globule of mercury in said tube, a crystal floating on said mercury and a vertically adj ustable conducting member extending down the tube into cont-act with the crystal.

Signed at Ottawa, Ontario, this 9th day of October, 1924.

NORMAN BRUCE DAVIS. 

